This invention is directed to a choke for attenuating interfering emissions which could otherwise be transmitted over an AC power line.
Some electronic equipment generates interfering emissions which are transmitted partly in the form of radiated RF interference and partly in the form of high frequency transients on the AC power line connected to the equipment. Digital computers and other equipment using switching type power supplies are two prime examples of equipment which generates such interfering emissions.
It is well known that interference which is radiated or which is transmitted via an AC power line unnecessarily clutters the RF spectrum and can interfere with other equipment using RF receivers. Because of the widespread use of switching power supplies and small computers, video games and the like, governmental regulations now impose stricter limitations on the amount of interfering emissions which such devices may emit.
To reduce the amount of interfering emissions which are transmitted via the AC power line, various types of filters have been used. In some cases, a filter in the form of a bi-filar wound toroid has been included in the equipment's power line. Bobbin wound chokes using two "C" ferrite cores have also been used to limit the interference transmitted via a power line.
Although some attenuation of the interference is achieved, such conventional approaches are not believed sufficient to reduce the interference to the point presently mandated by government regulations. Moreover, such conventional chokes tend to be undesirably large and expensive.